Effects of water content and salt content on electrical resistivity of loess

Abstract

As a special soil widely existing in world, loess engineering properties are often disturbed by water and salt. Hence, the influence of water content and salt content on the conductivity properties of loess was analyzed using the electrical resistivity of loess obtained by LCR digital bridge tester in this study. Loess electrical resistivity with different water content (8–20%) and NaCl content (0–6%) was obtained at test frequencies of 100 Hz, 1 kHz, and 10 kHz. Results show that loess electrical resistivity exhibited an exponential function with a change in water content. As water content increased, loess electrical resistivity decreased significantly. When water content exceeded the plastic limit, loess electrical resistivity decreased slowly. When NaCl content around 2%, the increase of ion content in conductive path of loess enhanced loess conductivity. When NaCl content reached 6%, the conductive capacity of the loess tended to reach its maximum, and the resistivity slowly decreased and stabilized. There was a nonlinear functional relation between loess electrical resistivity and test frequency. As the test frequency increased, the number of ions that could be used to form a conductive path increased, and loess electrical resistivity decreased. In addition, three paths model of loess electrical resistivity and double-layer structure can well explain above phenomena. This research can provide theoretical basis for electrical resistivity technology to predict water content and salt content, and valuable reference for large-scale field application of electrical resistivity observation technology.